Powered surgical tools, for example powered surgical saws and/or drills are powered tools that surgeons employ for performing certain surgical procedures that include cutting and/or drilling bones and/or other tissues. A powered surgical tool typically comprises a handpiece, or driver, in which is housed a motor, for example an electrically or pneumatically driven motor. The motor is attached, for example through a drive shaft, to a head of the driver, which is adapted to removably receive a surgical tool, for example a saw blade or a drill bit. Depending on the configuration of the driver and/or the nature of the attached tool, the actuation of the motor causes an oscillating or rotating movement of the head and thus of the tool.
Powered surgical tools are able to cut or drill through both hard and soft tissue much faster and with greater accuracy than manually operated tools. Powered surgical tools are furthermore able to perform specific cuts that manually operated tools are unable to perform. Also, the physical effort a surgeon has to employ to operate a powered surgical tool is much less than that used when cutting or drilling tissue, including bones, with a manual tool.
However, in order to provide enough power and/or torque to the tool for performing specific operations, the motor, in particular the electrical motor, is often dimensioned large relative to the tool, which in turn makes the driver housing the motor relatively bulky and thus sometimes inappropriate or at least inconvenient for delicate operations.
U.S. Pat. No. 5,993,454 for example describes a drill attachment for a surgical drill, which comprises a gear assembly for transferring the rotational power developed by the drill's shaft to a chuck mounted to the front of the drill attachment. From the figures, it seems that the drill attachment is coupled to the drill through a bayonet mechanism. The surgical drill illustrated in this document is however rather bulky. The drill comprises a motor and a gear train, but there is no indicating on how these elements are assembled and/or attached inside the surgical drill.
U.S. Pat. No. 5,207,697 describes a pistol-shaped surgical handpiece, in which a motor and a gear box, or reducer unit, are both inserted in a same cylindrical support shell. After its insertion into the shell, the motor is axially pressed between an intermediate baffle located inside the shell and a rear plug closing an extremity of the shell. The motor is thus axially fixed but fits radially loosely within the shell. This construction thus does not allow a precise positioning of the motor inside the handpiece, which is critical in order to achieve precise operations with the tools attached thereto. Furthermore, this attachment of the motor inside the shell requires the use of inrunner motors, which are bulkier than outrunner motor, because the motor is pressed by both extremities which must thus be static elements, i.e. part of an external stator.
German document DE 20 2007 004 491 U1 describes a surgical instrument using an outrunner motor. There is however no indication on how this solution is implemented. In particular, there is no indication on how the out runner motor is attached in the instrument or on how the outrunner is assembled with a gearbox in order to minimize the instrument's dimensions.